1. Field
The present invention relates to wireless communication systems, and more specifically to systems and techniques for detecting overload in a wireless communication system.
2. Background
Today, numerous different types of communication systems abound.
Wireless communication methods have gained great popularity in the past decade with the public. The appeal of wireless communications includes, among other things, the strong convenience factor of mobility. Another source of appeal is the ability to transmit data or voice communications without the need for cumbersome wiring or heavy equipment.
A number of different technologies have been pursued to implement wireless communications. These include systems based exclusively on Time Division Multiple Access (TDMA) schemes wherein the wireless communication channels between a base station and wireless communication devices (such as mobile telephones, laptop computers, handheld devices, and the like) are separated into discrete timeslots, each timeslot allowing for a particular communication device to transmit or receive data to or from the base station. Another popular system used extensively for wireless communications is based on Frequency Division Multiple Access (FDMA) techniques, where each wireless device transmits data on separate frequencies to distinguish the transmissions of one device from the other.
More recently, Code Division Multiple Access (CDMA) techniques have been introduced and are in widespread use commercially. The use of CDMA techniques in wireless communications has numerous advantages. Well-designed CDMA implementations can dramatically increase call quality, user capacity, data rates, and security, among offering other attributes. CDMA techniques are now prevalent in communication systems that employ fixed base stations within an access network to support communications with wireless communication devices. The CDMA communications system is a modulation and multiple access scheme based on spread-spectrum communications. In a typical CDMA communications system, a large number of signals share the same frequency spectrum. In accordance with CDMA techniques, several streams of information are each encoded using a unique code. It is these unique codes that allow the information to be transmitted over the same frequency band. Each information stream spread by a different code is commonly referred to as a “CDMA channel” or “code channel.” The coded information modulates a carrier signal, and thereby spreads the signal over a large bandwidth. The transmitted signals can be separated in the receiver by a demodulation process using a corresponding code to de-spread the desired signal. In short, whereas TDMA and FDMA rely on time and frequency channels to differentiate signals intended for different devices, CDMA relies on code channels for differentiation. The advantages of such a system are numerous, and include increased user capacity due to the fact that a number of communication streams can be simultaneously transmitted on the same frequency. Increased security, enhanced call quality, and high data rates are among other advantages that have been realized by CDMA technology.
In any wireless communications system, problems can occur when too many wireless communication devices are attempting to communicate with the same base station. A condition can be reached whereby the base station simply cannot accommodate the number of wireless communication devices attempting to access its resources. This condition is commonly referred to as overload. Overload can occur for a variety of reasons. Typically, overload occurs when one or more parameters are pronounced enough to result in placement of a “load” on the base station that, if sufficiently large, can effectively rob the base station of resources it needs to manage the ongoing communications.
In addition, depending on the causes of overload, different degrees of overload can occur. In particular, an overload condition may be severe enough to cause the termination of most or all communications between the base station and the wireless communication devices. Conversely, an overload condition may be less severe and can have minimal influence on the system. In the latter case, a need exists for detecting an early overload condition so that appropriate remedial measures may be taken as necessary to prevent an ensuing severe overload that would otherwise cause noticeable degradations in system performance.
Whatever the reason for overload, an effective communications system should have well-designed methods in place for detecting and managing overload. For optimizing performance, it is useful to detect overload conditions at the right instance. Detecting “overload” prematurely such as in situations where actual overload does not yet exist is problematic. Premature detection may result in the system taking remedial measures such as, for example, unnecessarily eliminating users of wireless communication devices from communicating with the base station that did not need to be eliminated in the first instance. Conversely, the failure to detect overload until the condition is severe—causing a corresponding failure to trigger timely remedial measures—can result in unnecessary communication failures between wireless communications devices and the base station. These failures can result in noticeable degradation in performance of the system by users of the remote stations.
Traditional overload detection schemes are hardly sophisticated enough to address these issues, much less provide an effective solution for any of them. They rely solely on considering the number of remote stations in communication with the base station at any given time. Where that number exceeds a static threshold, overload is detected. This method is insufficient and, more often than not, is grossly unreliable. First, the declaration of overload when a number of wireless devices communicating with a base station sector exceeds an arbitrary threshold, without additional information, is not an accurate indication that an actual overload condition based on real performance-related factors exists.
Further, this traditional method does not distinguish the severity of the detected overload condition. In the traditional method, overload either exists or it does not. Use of this scheme provides no measure for detecting early signs of threshold and thereby providing appropriate remedial measures before more serious overload occurs, potentially causing significant and noticeable degradation in communications that could have been avoided from the outset by early detection. As such, the traditional method does not employ any scheme for identifying minor overload problems that could otherwise be corrected or minimized through appropriate management, thereby avoiding more severe overload.
In short, this traditional detection scheme is problematic, oversimplified, and more often than not, is not indicative of whether an actual overload condition based on real world parameters exists.